Benchmark: 
running
 a_1, a_2
 for at least 5 CPU seconds
...

       a_1:  5 wallclock secs ( 4.98 usr +  0.08 sys =  5.06 CPU) @ 68.58/s (n=347)

       a_2:  5 wallclock secs ( 5.24 usr +  0.00 sys =  5.24 CPU) @ 74.62/s (n=391)

      Rate a_1 a_2
a_1 68.6/s  -- -8%
a_2 74.6/s  9%  --
Benchmark: 
running
 a_1, a_2
 for at least 60 CPU seconds
...

       a_1: 60 wallclock secs (59.26 usr +  0.84 sys = 60.10 CPU) @ 70.72/s (n=4250)

       a_2: 63 wallclock secs (62.98 usr +  0.00 sys = 62.98 CPU) @ 74.63/s (n=4700)

      Rate a_1 a_2
a_1 70.7/s  -- -5%
a_2 74.6/s  6%  --